The field of the present invention is apparatus and methods for the surgical implantation of granular substances. A number of injuries, diseases and other conditions are known to the medical and dental sciences which can cause atrophy of the bones forming the alveolar ridges of the human upper jaw (maxilla) and lower jaw (mandible). When alveolar ridge atrophy is sufficiently far advanced, the patient may even be unable to wear dentures because the ridges are insufficient to anchor them. In such cases, and in other situations where it is deemed medically desirable to arrest or repair alveolar ridge injury or deterioration, various surgical procedures can be employed to augment the alveolar ridges.
A traditional procedure for alveolar ridge augmentation is known as the "fifth rib" procedure, wherein each of the patient's fifth ribs is removed and bone therefrom engrafted upon the alveolar ridges. The "fifth rib" procedure involves major surgery, the disadvantages of which include not only substantial expense and patient discomfort but also a risk of infection and other complications that is multiplied by the fact that the procedure necessarily involves multiple surgical sites.
An alternative to the "fifth rib" procedure, employed with increasing frequency and success in recent years, involves the use, instead of bone from the patient's ribs, of granules of a biocompatible ceramic substance having a unique pore structure that supports and encourages the ingrowth of the patient's own maxillar and mandibular bones. Ceramics known to have suitable biocompatability properties include hydroxyapatite, whitlockite, and alpha alumina. See, e.g.: Jarcho, M.: "Calcium Phosphate Ceramics As Hard Tissue Prosthetics", Clin. Orthoped. 157: 259 (1981); Rothstein, S. et al., "Use of Hydroxyapatite for the Augmentation of Deficient Alveolar Ridges", J. Oral Maxillofac. Surg. 42: 2, 224-230 (1984); Kent, J. et al., "Reconstruction of the Atrophic Alveolar Ridge With Hydroxyapatite: A Five Year Report", Study presented at the Second World Congress of Bio-materials, Washington, D.C., Apr. 27-May 1, 1984; Cohen, D. W., ed., "Report of a Clinical Conference on a New Implant Material for Ridge Augmentation and Preprosthetic Preparation of the Edentulous Patient", The Compendium of Continuing Education in Dentistry, Suppl. No. 2, S45-S86 (1982).
By the use of certain hydrothermal chemical exchange processes, carbonate skeletal materials from certain specific marine organisms can be converted into hydroxyapatite or whitlockite replicas that retain a structure of completely interconnecting pores whose dimensions closely approximate those of human cancellous bone. The characteristics of these materials and methods of making them are disclosed in Roy, U.S. Pat. No. 3,929,971. Related technologies are disclosed in White, et al., U.S. Pat. No. 3,890,107.
Preparations of porous biocompatible ceramics, in granular form suitable for surgical implantation, are now commercially available to oral surgeons through several suppliers.
The use of ceramic granule implants has several advantages over the "fifth rib" procedure: it is not only less expensive and less painful, but because it involves fewer surgical sites, it lessens the risk of infection and other complications.
An early but still-used technique for applying growth-supporting ceramic substances to the maxilla and mandible involves incisions through the gum tissue along the whole length of the area to be augmented. The bone is then typically scraped until a fresh bleeding surface is exposed, the ceramic deposited in granular form and the gum tissue sutured over the deposit.
The most recent technique involves the use of syringes to implant the ceramic substances in granular form at sites along the alveolar ridges remote from the incision sites. The advantage of this technique over the earlier implantation technique is that it involves smaller incisions, and less suturing, resulting in less tissue trauma, less patient discomfort and lower risk of infection and other complications.
In the syringe implantation technique, the ceramic substance in granular form is usually mixed within the syringe with a saline solution or with blood taken from the patient. The syringe typically includes a hollow, cylindrical barrel with an opening at each end. A plunger is slidably inserted into an opening at the distal end of the barrel. There is typically a porous filter over the opening at the distal end of the barrel which prevents the granules from escaping but allows liquids to enter the barrel. After the ceramic granules and the liquid are mixed, the filter is removed so that the mixture can be extruded from the syringe.
A tunnel is then surgically formed under the periosteum of the maxilla or mandible to be augmented. The delivery of the ceramic granule/liquid mixture to the alveolar ridge repair site requires one or more incisions. Though the location of the incision depends upon the particular repair, an incision is typically made near the canine teeth in mandibular augmentation and at the mid-line of the gum, as viewed from above, in maxillar augmentation. Following tunnel formation, the distal end of the syringe barrel is inserted into the sub-periosteal tunnel and is guided to the location, remote from the incision, where the augmentation is to begin. As the syringe is withdrawn through the sub-periosteal tunnel, its contents are gradually extruded, leaving the sub-periostel tunnel packed with the ceramic granule mixture. After the syringe is fully withdrawn, the incision is sutured closed and the deposited ceramic granules may, if necessary, be manipulated into optimal position.
While guiding the syringe along the sub-periosteal tunnel, the surgeon must take great care to avoid puncturing the periosteum or the overlying gum tissue. Where the augmentation site is remote from the incision, it is difficult to avoid puncture if a conventional straight syringe barrel is used. The reason is that the alveolar ridge, viewed from above or below, is not straight but curved, describing an approximate semi-circle. Thus, when the ceramic granule mixture is to be deposited at a site on the posterior portion of the ridge, the syringe barrel, at the point of incision, must be flexed outward against the tissue so that the distal opening will follow as closely as possible the curve of the ridge. The flexing may tear the tissue at the incision, or necessitate a larger incision or additional incisions. If the syringe is not flexed outward at the incision, then the distal end of the syringe barrel, as it moves toward the posterior part of the ridge, will be pushed increasingly outward against the periosteum and the gum tissue and will likely result in tearing of those tissues. The mandibular ridge is curved in an even more complex fashion than the maxillar ridge. The mandibular ridge is not only roughly semicircular when viewed from above or below, but is seen to arch upward posteriorly as viewed from the side. Thus, the problems encountered in using the conventional straight syringe are even more acute in mandibular surgery than in maxillar surgery.
Presently on the market are several brands of ceramic granules intended for use in alveolar ridge augmentation and other periodontal repairs. Implantation syringes are typically sold together with the granules, which are packaged either in separate ampules or within pre-filled, sterilized syringes. Common elements of all now-available syringes are a simple, straight barrel configuration and a straight tip, that is, a tip truncated at a right angle to the longitudinal axis of the barrel. No supplier currently offers a granule implantation syringe that is in any wise adjustable in terms of barrel curvature or tip configuration, nor does any supplier currently offer an array of syringes which differ in barrel curvature or tip configuration. Nor does any presently-available granule implantation syringe contain any means for varying the orientation of the barrel with respect to the finger support component.